Also make sure we use the same case in the GuI: VirtIO, and
explain why IO Thread requires a specific controller option.
---
qm.adoc | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/qm.adoc b/qm.adoc
index 85b939a..ec57f01 100644
--- a/qm.adoc
+++ b/qm.adoc
@@ -143,15 +143,20 @@ connected. You can connect up to 6 devices on this
controller.
hardware, and can connect up to 14 storage devices. {pve} emulates by default a
LSI 53C895A controller.
+
-A SCSI controller of type _Virtio_ is the recommended setting if you aim for
+A SCSI controller of type _VirtIO SCSI_ is the recommended setting if you aim
for
performance and is automatically selected for newly created Linux VMs since
{pve} 4.3. Linux distributions have support for this controller since 2012, and
FreeBSD since 2014. For Windows OSes, you need to provide an extra iso
containing the drivers during the installation.
//
https://pve.proxmox.com/wiki/Paravirtualized_Block_Drivers_for_Windows#During_windows_installation.
+If you aim at maximum performance, you can select a SCSI controller of type
+-VirtIO SCSI single- which will allow you to select the *IO Thread* option.
+When selecting -VirtIO SCSI single- Qemu will create a new controller for
+each disk, instead of adding all disks to the same controller.
+
* The *Virtio* controller, also called virtio-blk to distinguish from
-the Virtio SCSI controller, is an older type of paravirtualized controller
+the VirtIO SCSI controller, is an older type of paravirtualized controller
which has been superseded in features by the Virtio SCSI Controller.
[thumbnail="gui-create-vm-hard-disk.png"]
@@ -190,10 +195,12 @@ emulated SCSI controller will relay this information to
the storage, which will
then shrink the disk image accordingly.
.IO Thread
-The option *IO Thread* can only be enabled when using a disk with the *VirtIO*
controller,
-or with the *SCSI* controller, when the emulated controller type is *VirtIO
SCSI*.
-With this enabled, Qemu uses one thread per disk, instead of one thread for
all,
-so it should increase performance when using multiple disks.
+The option *IO Thread* can only be used when using a disk with the
+*VirtIO* controller, or with the *SCSI* controller, when the emulated
controller
+ type is *VirtIO SCSI single*.
+With this enabled, Qemu creates one I/O thread per storage controller,
+instead of a single thread for all I/O, so it increases performance when
+multiple disks are used and each disk has its own storage controller.
Note that backups do not currently work with *IO Thread* enabled.
--
2.1.4
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